1Laboratory of Phytopathology, Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80--822 Gdansk, Poland; 2Laboratoire de Genetique Moleculaire des Microorganismes, UMR-CNRS 5577, INSA, Bat. 406, 20, Av. A. Einstein, 69621 Villeurbanne cedex, France
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Accepted 14 June 1999.
Erwinia chrysanthemi mutants, containing transcriptional fusions of one of the minor pectate lyase genes (pelI, pelL, pelZ) with the reporter gene encoding β-glucuronidase activity, were studied for their ability to cause disease symptoms and to synthesize pectinases after inoculation of potato tubers. The strains affected in pelI and pelL genes displayed reduced virulence on potato tubers, demonstrating the important role of these isoenzymes in soft rot disease. Inactivation of the pelZ gene slightly influences the ability to macerate. Analysis of the bacterial population showed rapid multiplication of bacteria during infection. Similar kinetics of growth were observed for all mutants and for the wild-type strain. Comparison of the mutants and the wild-type strain showed that the pelI, pelL, and pelZ mutants synthesized reduced levels of Pels. The expression of pelZ is fivefold higher in planta than in bacterial cultures. In contrast, both pelI and pelL are highly (10-fold factor) induced in planta, which is characteristic of the plant-inducible pectate lyases.
© 1999 The American Phytopathological Society